1. Field of the Invention
The invention relates to the field of variable clearance engines. The engine system also qualifies as an advanced reciprocating mechanism which refers to the fact that the movement of the piston is not entirely dependent on the simple harmonic motion induced by rotation of the crankpin.
2. Description of Prior Art
The crank radius of the conventional crankshaft is fixed and therefore the crankpin follows a circular path about the axial center of rotation of the main shafts. In this invention each throw of the crankshaft contains two crankpins. One of these crankpins, which is called the "primary crankpin", is fixed to the crank arm. The second crankpin is pivotally mounted on the primary crankpin by a disc shaped linkage and subscribes a quarter arc about the primary crankpin. The second crankpin is called the secondary transfer crankpin because it transfers loads to and from the piston to the crank arm. In pivoting about the primary crankpin the secondary transfer crankpin changes the effective crank radius. Most generally the secondary transfer crankpin is in the pivotal position which presents the shortest crank radius on the upstroke of the piston and then pivots to the position which presents the longest crank radius when the piston beings the downstroke. Operation in this manner improves the mechanical conversion process during the power stroke and decreases the pumping losses during the compression stroke.
In previous engines of the character described eccentrics have been used in conjunction with the crankshaft. Although the transfer linkage between the primary crankpin and the secondary crankpin is circular in shape it should not be confused with an eccentric. By definition an eccentric is a circular member in which the geometric center rotates about the eccentric center. In this application, as previously stated, the axial center of the secondary transfer crankpin rotates about the axial center of the primary crankpin. The transfer linkage is made circular so that the connecting rod can be mounted directly upon it and thus shorten the length of the secondary transfer crankpin. When the transfer linkage is not circular in shape the connecting rod must be mounted adjacent to the transfer linkage on the secondary transfer crankpin thus making it necessary to lengthen the secondary transfer crankpin.